The developing field of neural stimulation and recording generally involves the application or measurement of electrical signals associated with nerves and muscles to induce or measure specific physiological responses. The field has developed to support a variety of applications, including, but not limited to, neuromuscular control, optical prostheses, pain therapy, and morbid obesity treatment. In this field, “cuff” electrodes which may contact, engage, or partially or completely surround a nerve fiber or branch to be stimulated or monitored, may often be used. The use of neural stimulation and recording in such situations provides a minimally invasive, reversible treatment requiring minimal post-operative care as opposed to highly invasive, non-reversible and expensive surgical alternatives.
Neural stimulation and recording techniques for controlling, interpreting and treating numerous pathological conditions may utilize a periodic or constant electrical stimulation or reading of specific nerves, nerve fibers and muscles by one or more electrodes. Numerous electrode designs have been developed to date for applications involving functional electrical stimulation of nerves and nerve fibers. One of the most commonly employed electrode designs is the cylindrical cuff electrode. This design is simple and relatively easy to use for long term use in subjects even when they are moving. Cylindrical cuff electrodes are well suited for use with nerves due to the geometry of a typical nerve or nerve fiber, which is considered to be cylindrical from a design perspective. Some examples of cuff electrodes may be found in U.S. Pat. Nos. 6,600,956, and 8,983,626, and U.S. Patent Application Publication Nos. 2013/0085359 and 2010/0168831 the entire content and disclosure of each of which is incorporated herein by reference. One of the barriers to widespread use of these cuff electrodes is the lack of fabrication techniques that provide scalable commercial production. Existing cuff electrodes are generally fabricated only at a scale suitable to larger nerves and muscles and many cuff electrodes are designed based on components that would be difficult or impossible manufacture at a highly reduced scale for fitment to small nerves and muscles.
As an example, one of the current methods of manufacturing cuff electrodes is through manual casting. Manual casting produces small production quantities and does not generally lend itself to mass fabrication of reduced scale cuff electrodes.
Alternate manufacturing techniques of fabrication processes for implantable neural interface devices may include, for example, additive manufacturing, stamping, casting, injection molding, photolithography, and subtractive manufacturing, however each of these has drawbacks.
Additive Manufacturing
Additive manufacturing describes a process where a part or parts are formed by accumulating and fusing material together, typically in a layer-on-layer manner that builds 3D objects by adding layer-upon-layer of material, whether the material is plastic, metal, concrete or human tissue. Common additive manufacturing technologies may include or utilize features such as computers, 3D modeling software, machine equipment, and layering material. The term additive manufacturing encompasses many technologies and may include subsets such as, for example, 3D Printing, Rapid Prototyping (RP), Direct Digital Manufacturing (DDM), layered manufacturing and additive fabrication. See, e.g., U.S. Pat. No. 9,352,421, U.S. Patent Publication No. 2016/0276056, and International Patent Application Publication WO2015/012469 the entire content and disclosure of each of which is incorporated herein by reference. The use of additive manufacturing techniques like 3-D printing produces cuffs at a low rate, similar to that of manual casting, and does not generally lend itself to mass fabrication of reduced scale cuff electrodes.
Stamping
Stamping (also known as pressing) is the process of placing flat sheet material in either blank or coil form into a stamping press where a tool and die surface forms the material into a net shape. Stamping includes a variety of sheet-material forming manufacturing processes, such as, for example, punching using a machine press or stamping press, blanking, embossing, bending, flanging, and coining. A stamping process is usually carried out on sheet metals, but can also be used on other materials, such as polymers. Examples of applications of sheet material stamping include electrical connectors, micromeshes, microswitches, microcups, wristwatch components, handheld device components, and medical devices. See, e.g., U.S. Pat. No. 7,397,631 the entire content and disclosure of which is incorporated herein by reference.
Casting
Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting materials are usually metals or various cold setting materials that cure after mixing two or more components together. Some examples of casting materials include epoxy, concrete, plaster, ceramic and clay. Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods. See, e.g., U.S. Patent Application Publication No. 2015/0072163 the entire content and disclosure of which is incorporated herein by reference.
Role to Role Printing
Roll-to-roll printing, also known as web printing, reel-to-reel processing or R2R, is the process of creating electronic devices on a roll of flexible plastic or metal foil. In other fields predating this use, it can refer to any process of applying coatings, printing, or performing other processes starting with a roll of a flexible material and re-reeling after the process to create an output roll. These processes can be grouped together under the general term converting. When the rolls of material have been coated, laminated or printed they are normally slit to their finished size on a slitter rewinder. See, e.g., U.S. Pat. Nos. 8,128,393 and 9,340,001 the entire content and disclosure of each of which is incorporated herein by reference.
Injection Molding
Injection molding is a manufacturing process for producing parts by injecting material into a mold. Injection molding can be performed with a host of materials, including metals, (for which the process is called die-casting), glasses, elastomers, confections, and most commonly thermoplastic and thermosetting polymers. Material for the part is fed into a heated barrel, mixed, and forced into a mould cavity, where it cools and hardens to the configuration of the cavity. Molds are generally made from metal, usually either steel or aluminum, and precision-machined to form the features of the desired part. Injection molding is widely used for manufacturing a variety of parts, from the smallest components to entire body panels of cars. See, e.g., U.S. Pat. No. 7,618,577 the entire content and disclosure of which is incorporated herein by reference.
Photolithography
Photolithography, also termed optical lithography or UV lithography, is a process used in microfabrication to pattern parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical “photoresist”, or simply “resist”, on the substrate. A series of chemical treatments then either engraves the exposure pattern into, or enables deposition of a new material in the desired pattern upon, the material underneath the photo resist. For example, in complex integrated circuits, a modern CMOS wafer will go through the photolithographic cycle up to 50 times. See, e.g., U.S. Pat. No. 6,982,232 the entire content and disclosure of which is incorporated herein by reference.
Subtractive Manufacturing
Subtractive manufacturing, often referred to as machining, is any of various processes in which a piece of raw material is cut into a desired final shape and size by a controlled material-removal process. The processes that have this common theme, controlled material removal, are today collectively known as subtractive manufacturing, in distinction from processes of controlled material addition, which are known as additive manufacturing. Exactly what the “controlled” part of the definition implies can vary, but it almost always implies the use of machine tools (in addition to just power tools and hand tools). Subtractive manufacturing is a part of the manufacture of many metal products, but it can also be used on materials such as wood, plastic, ceramic, and composites. See, e.g., International Patent Application Publication WO2014/189371 the entire content and disclosure of which is incorporated herein by reference.